A Phase II Clinical Study on Apatinib Plus Vinorelbine in Refractory HER2-Negative Breast Cancer and its Metabolic Implications of Drug Resistance

Background: Apatinib, a tyrosine-kinase inhibitor that targets the vascular endothelial growth factor receptor 2, contributes to the inhibition of angiogenesis. Vinorelbine, a semisyn-thetic vinca alkaloid, primarily inhibits metaphase mitosis of cancer cells through its interactions with tubulin. This study aimed to evaluate whether apatinib combined with vinorelbine was ef-fective and safe for refractory human epidermal growth factor receptor 2 (HER2)-negative breast cancer patients who failed taxanes and/or anthracycline and analyze the possible mechanism of drug resistance through metabolomic analysis. Methods: Eligible patients were HER2-negative, inoperable, locally advanced, or metastatic breast cancer patients who progressed after at least one chemotherapy regimen in this present prospective phase II study. Patients took oral apatinib (250-500 mg/day) plus intravenous infusion of vinorelbine (25 mg/m2 on day 1, day 8 at 3-week intervals). Objective response rate (ORR) was our primary endpoint, while disease control rate (DCR), overall survival (OS), progression-free survival (PFS), and toxicity were our secondary endpoints. The exploratory purpose was to identify biomarkers or drug resistance mechanisms through metabolomics changes before and after the combination therapy. Results: Between September, 2019 and June, 2022, a total of 34 patients were included. ORR and DCR were 32.4% (11/34) and 85.3% (29/34), respectively. The median PFS was 5.0 months (95% CI, 3.766-6.234), while the median OS was 13.0 months (95% CI, 8.714-17.286). Side effects included hematologic toxicity, gastrointestinal reaction, and sinus tachycardia, which were mild to moderate. The mainly disturbed metabolic pathways were the cAMP signaling pathway, the alanine/aspartate/glutamate metabolism, the central carbon metabolism in cancer, the beta-alanine metabolism, the butanoate metabolism, and the glyoxylate and dicarboxylate metabolism, which may lead to the resistance of patients to this combination therapy. Conclusion: Apatinib combined with vinorelbine is effective and safe in patients with locally advanced or metastatic refractory HER2-negative breast cancer. The findings of this study con-tribute to a better understanding of the metabolic effect of apatinib and vinorelbine therapy.